This application is related to Japanese Patent Applications No. 2000-387624 filed on Dec. 20, 2000, No. 2000-392789 filed on Dec. 25, 2000, No. 2000-395529 filed on Dec. 26, 2000, No. 2000-395530 filed on Dec. 26, 2000, No. 2001-251898 filed on Aug. 22, 2001, and No. 2001-253237 filed on Aug. 23, 2001, the contents of which are hereby incorporated by reference.
1. Field of the Invention
The present invention relates to an electromagnetic clutch for transmitting and interrupting a driving force from a driving source to a driven device. The present invention is suitably used for an electromagnetic clutch for transmitting and interrupting a driving force of a vehicle engine to a rotation unit in an engine component, such as an oil pump and a compressor.
2. Description of Related Art
A conventional electromagnetic clutch described in JP-U-6-30535 includes a rotor rotated and driven by a driving source such as an engine, an armature disposed to have a predetermined clearance with the rotor, and an electromagnetic coil for generating an electromagnetic force between the armature and the rotor. In addition, the armature is fixed to a center hub connected to a shaft of the compressor, the rotor is assembled to a front housing of the compressor through a bearing, and the electromagnetic coil is assembled to a plate fixed to the front housing. Accordingly, in this clutch structure, plural assembling steps at least more than three are necessary, and it is difficult to reduce assembling process.
On the other hand, in conventional clutch structures, there may be caused regarding problems such as an increased clearance between a stator housing and a rotor, an oil adhesion on an electromagnetic clutch during an engine inspection or during an oil addition, a noise generation and the like.
In view of the foregoing problems, it is an object of the present invention to reduce assembling steps of an electromagnetic clutch.
It is an another object of the present invention to provide an electromagnetic clutch which prevents a clearance between a rotation member such as a rotor, and a holding member for holding an electromagnetic coil from becoming larger.
It is a further another object of the present invention to prevent an oil from being adhered onto an armature of the electromagnetic clutch.
It is a further another object of the present invention to provide an electromagnetic clutch which can prevent a noise generated when an armature, a plate spring and the like collide with each other.
It is a further another object of the present invention to provide an electromagnetic clutch which reduces a noise without using a cover covering the whole electromagnetic clutch.
According to the present invention, in an electromagnetic clutch for transmitting and interrupting a driving force of a driving source to a driven device, a driving-side rotation member is disposed to be rotated by the driving source, a driven-side rotation member is disposed rotatably to be connected to a side of the driven device, an electromagnetic coil is disposed for generating an electromagnetic force when being supplied with power, and an armature is connected to one of the driving-side rotation member and the driven-side rotation member. The armature has a friction surface which contacts the other one of the driving-side rotation member and the driven-side rotation member by the electromagnetic force generated from the electromagnetic coil, to transmit the driving force from the driving-side rotation member to the driven-side rotation member. In the electromagnetic clutch, the driven-side rotation member and the electromagnetic coil are assembled to the driving-side rotation member through a bearing member. Accordingly, by assembling the driving-side rotation member to a shaft of the driving source, the assembling operation of the electromagnetic clutch to the driving source is finished, and assembling steps of the electromagnetic clutch to the driving source can be finished. As a result, assembling steps of the electromagnetic clutch to the driving source can be reduced.
Preferably, a holding member for holding the electromagnetic coil is fixed through a bushing made of an elastic material. Therefore, it can absorb a relative vibration displacement of the holding member relative to the rotation member, generated due to a vibration of a member to which the holding member is fixed, and can absorb a dimension differences of the holding member and the rotation member. Accordingly, a suitable clearance between the holding member and the rotation member can be maintained.
Further, the driving-side rotation member, the driven-side rotation member and the armature are disposed so that a rotation axis of the armature is substantially parallel, a wall surface is provided in a ring shape to enclose the armature at an outer radial side of the armature, and the wall surface is substantially parallel to each rotation axis of both the driving-side rotation member and the driven-side rotation member. Therefore, even when an oil drops onto the electromagnetic clutch in an engine checking operation or in an engine oil addition, dropped oil flows downwardly along the wall surface without flowing toward the armature. Alternatively, a circular recess portion is recessed in an approximate U-shape in cross section in a rotation axial direction of both the driving-side rotation member and the driven-side rotation member, to enclose the armature at an outer radial side of the armature. Therefore, even when the oil drops onto the electromagnetic clutch, the dropped oil flows downwardly along the recess portion from the electromagnetic clutch, and an oil adhesion on the armature of the electromagnetic clutch can be prevented. Alternatively, an inner peripheral wall surface of the armature is provided with a taper portion tapered in such a manner that a diameter of the inner peripheral wall surface is enlarged as toward a side opposite to the friction surface. Therefore, oil moving to the inner peripheral wall surface flows to the side opposite to the friction surface, and falls from the electromagnetic clutch.
Preferably, a spring member is disposed to be partially connected to the armature, for generating an elastic force for separating the armature from the other one of the driving-side rotation member and the driven-side rotation member. Further, a damper member for absorbing a collision shock is disposed on at least one side of an opposite portion of the spring member, opposite to the armature, and an opposite portion of the armature, opposite to the spring member. Accordingly, it can prevent a direct collision between the armature and the spring member at a time where the electromagnetic clutch is turned off, and it can restrict a collision noise from being caused.
Preferably, a vibration-restriction member for absorbing vibration of the armature is disposed to be fixed to the armature. Because the vibration of the armature can be absorbed, a noise due to the vibration of the armature can be reduced without using a cover covering the whole electromagnetic clutch. More preferably, the vibration-restriction member is fixed to the armature through a bonding member made of a visco-elastic material. Therefore, the noise due to the vibration of the armature can be further reduced without using a cover covering the whole electromagnetic clutch.